不依托第三方插件实现的php原生上传图片的方法，操作步骤如下。

1、在当前主题或者当前插件的目录下，创建新文件script/upload.js，写入代码

!function(o){
    var b=$('body');
    function upload(){
        var id='ajax_upload'+new Date().getTime(),d = $(this);;
        b.append(`<input type="file" id="${id}" accept="${o.accept}" style="display:none">`);
        var el=$('#'+id);
        b.one('change','#'+id,function(){
            var f = new FormData();
            f.append('file',$(this)[0].files[0]);
            $.ajax({
                url: ajaxurl+o.src,
                type: 'POST',
                dataType: 'json',
                data: f,
                contentType: false,
                processData: false,
                xhr: function() {
                    var xhr = new XMLHttpRequest(),t;
                    xhr.upload.addEventListener('progress', function (e) {
                        if (e.lengthComputable) {
                            t = Math.floor(e.loaded / e.total * 100);
                            o.progress && o.progress(d, t);
                        }
                    });
                    return xhr;
                },
                success:function(r){
                    o.success(d, r);
                },
                error:function(r){
                    o.error && o.error(d,r);
                }
            });
        }),
        el.click();
    }
    b.on('click',o.click,upload);}({
    src: 'ytecn_ai_xzjt',  //这里AppName改为你的应用ID
    click: '.ytecn_upimgbutton',
    accept: '.jpg,.jpeg,.png,.gif,.bmp,.svg',
    success: function(e, r){
        console.log('上传成功，图片链接：'+r.url);
        e.siblings('.ytecn_input_img').attr("value", r.url);
        e.siblings('img').attr('src',r.url);
        e.val('选择文件');
    },
    error: function(e){
        alert('上传失败');
    },
    progress: function(e,n){
        e.val('上传进度：'+n+'%');
    }});

2、通过Filter_Plugin_Cmd_Ajax添加ajax异步上传

function ActivePlugin_ytecn_ai_xzjt() {
    Add_Filter_Plugin('Filter_Plugin_Cmd_Ajax', 'ytecn_ai_xzjt_Cmd_Ajax');                }function ytecn_ai_xzjt_Cmd_Ajax($src){
    global $zbp;
    if ($src == 'ytecn_ai_xzjt') {
        if (!$zbp->CheckRights('UploadPst')) {
            $zbp->ShowError(6);
        }
        Add_Filter_Plugin('Filter_Plugin_Upload_SaveFile', 'ytecn_ai_xzjt_Upload_SaveFile_Ajax');
        $_POST['auto_rename'] = 1;
        PostUpload();
        echo json_encode(array('url' => $GLOBALS['tmp_ul']->Url));
        exit;
    }}function ytecn_ai_xzjt_Upload_SaveFile_Ajax($tmp, $ul){
    $GLOBALS['tmp_ul'] = $ul;}

3、在需要的地方调用，比如在文章编辑页面。

function ActivePlugin_ytecn_ai_xzjt() {
    Add_Filter_Plugin('Filter_Plugin_Edit_Response5','ytecn_ai_xzjt_edit_response');                 }function ytecn_ai_xzjt_edit_response() {
    global $zbp, $article;
    echo '<script type="text/javascript" src="' . $zbp->host . 'zb_users/plugin/ytecn_ai_xzjt/script/upload.js"></script>';
    echo '<style type="text/css">
        .ytecn_input_img{width:40%!important;}
        .ytecn_upimgbutton{ width:120px;}
        .ytecn_upimg{width:100px;vertical-align: middle;}</style>';
    echo '<div id="tesetu">缩略图1：    <input name="meta_pic" id="edtTitle" type="text" class="ytecn_input_img" value="' . $article->Metas->tesetu1 . '" />
        <input type="button" class="ytecn_upimgbutton" value="选择图片">
        <img class="ytecn_upimg" src="' . $article->Metas->pic. '">
        </div>';
    echo '<div id="tesetu">缩略图2：    <input name="meta_pic2" id="edtTitle" type="text" class="ytecn_input_img" value="' . $article->Metas->tesetu2 . '" />
        <input type="button" class="ytecn_upimgbutton" value="选择图片">
        <img class="ytecn_upimg" src="' . $article->Metas->pic2. '">
        </div>';}